1988 Merc Grand Marque EGR valve


Old 03-15-07, 08:10 PM
Thread Starter
Join Date: Mar 2001
Posts: 34
1988 Merc Grand Marque EGR valve

88 merc grand marque, 5.0 L, FI, air, etc. Recently developed following symptoms: rough idle, stalling, hard to start, choppy while normal driving.

Whats been done: new plugs, rotor, plug wires, coil, fuel filter, air filter, EGR vlave. Still has same symptoms. It all goes away when the vacuum line is disconnected from EGR valve. The valve is new, so I am wondering if there is something plugged in the air plenum that it attaches to. Is this possible? Is there something going on here I am missing? Not really sure how the EGR valve works or what its function is. Any ideas would be appreciated. Thanks in advance.

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Old 03-15-07, 11:24 PM
Join Date: Feb 2007
Posts: 87
The e.g.r valve recuirculates exhaust gases from the exhuast to the intake (major horse power robber), check your p.c.v valve on one or both of your rocker covers, they are about $2.50-$5.00 a piece.
Old 03-16-07, 07:54 AM
Join Date: Mar 2007
Location: usa
Posts: 162
i belive thats a 5.0 fi if you take the rubber hose off the plenum [air intake] there is a small hole that the gets clogged take the valve out clean with carb clean note: there are special carb cleans for the teflon coating on the plenam parts. the valve is held in with two screws be careful i think there is a gasket under it or oring. clean from valve through the little hole it'll run like new

Last edited by e150club; 03-16-07 at 08:43 AM.
Old 03-16-07, 12:43 PM
Thread Starter
Join Date: Mar 2001
Posts: 34
Thanks for the info, I will change the pvc valve and check the air passage in the plenum this weekend. Will it do any harm to leave the vacuum line unplugged in the meantime? It runs fine with it unplugged. Could it cause any harm to the computer or other systems? Thanks again.

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